1. Field of the Invention
The present invention concerns mobile radio systems and in particular mobile radio systems offering, in addition to a telephone service, a data transmission service, in particular a service for transmission of data in the form of short messages and therefore intended more particularly for mobile terminals.
2. Description of the Prior Art
One example of such systems is the GSM system (Global System for Mobile communications).
This system offers an SMS-PP service (Short Message Service-Point to Point) for transmitting messages between two users, one of whom is a user of the GSM network and the other of whom can be a user of the GSM network or a user of another network also offering data transmission services.
The SMS-PP short message transmission service is defined in GSM Recommendations 03.40 and 04.11.
This system additionally offers a service for broadcasting from the network itself short messages bearing information of general interest, for example information on road traffic or on the weather, known as the SMS-CB service (Short Message Service-Cell Broadcast).
This SMS-CB short message broadcast service is defined in GSM Recommendation 03.41.
One aim of the present invention is to provide, in a mobile radio system such as the GSM system in particular, a new type of service consisting in a service for transmitting point to multipoint type messages between users of the network, in other words enabling a user of the network to broadcast information to a set of other users of the network. Examples of applications of a point to multipoint service of this kind include updating in real time by the users themselves of the information broadcast by means of the SMS-CB service, the possibility of communicating with a user group ("group communication" type application), the possibility of communicating incognito with other users, etc.
Another aim of the present invention is to provide a point to multipoint service of this type at lower cost by making optimum use of existing infrastructures.